Would you want to get up close and personal with someone who'd cut your bits off ?

But seriously....... I can't say I've heard of that before

Most of mine are 'done' at 6 weeks, but we did have one who went at 5 months and I don't really find it makes much of a difference. If anything they are soppier afterwards than before

It sounds like something maybe happened at the vets which has given them a scare

They're smarter than most folks think

I'd just spend a bit of time with them, getting them used to contact again and reassuring them that humans are a good thing.
Hope they get back to being friendlier soon
Karen x